Fallen victim to blazer bug

Well I got bit by the problem bug 2nite....lets start off I had the irratic fuel gauge when I would have my turn signal iknew what time it was but it would still run fine but 2day I my truck spit out the battery light n the voltage gauge was at or lower than half way between 9 and 14 so I took it to get the code n they tell me to come back in the morn because they don't check after dark the truck sits for bout 20 to 30 min and it started up but I could tell it was struggling so it fires up but when it pulled voltage (i'd turn on my hazards) the motor would lope with the hazards...then when I went to pull off it would cut out...it runs in neutral but dies in drive....also I realized tht my dome light blew don't know if that had anything to do with it...also 1st start it would crank up after two tries everytime but after 1st it'd start right up

The alternator has been tested twice once on a autometer tester at one autozone results say bad take it to the bigger autozone down the street tells me its fine when tested with a bigger unit...battery was fine before last nite...now runtime may have been a determining factor between the 2 tests...but I'm lost....no truck for me

i have to get a new alternator which i had already planned from the confusion but it got put off a week too long...have you tried to start it with a jump if it runs and when you raise the rpms and the alternator doesnt charge the battery that may just be the prob...like right now mine wont start but when i jump it or put a fresh battery in it will crank right up